This invention relates to a cylindrical lockset for operating a latch bolt retractor assembly mounted in a door, and particularly to a motorized lock actuator for electrically locking and unlocking the cylindrical lockset. More particularly, this invention relates to a door-mounted cylindrical lockset having an outside door handle that can be locked against rotation using an electromechanical lock actuator mechanism mounted in the lockset, thereby preventing an intruder from opening the door by rotating the outside handle to retract a latch bolt mounted in the door and connected to the lockset.
Cylindrical locksets are well known and such a lockset is operated to lock and unlock a door by rotating inside and outside door knobs or lever handles connected to the lockset. Typically, a cylindrical lockset is used to connect a door handle to a retractable latch bolt. Each cylindrical lockset can include various mechanical linkages and locking mechanisms of the types described in the following paragraphs.
In use, a user can often rotate either the inside or outside door handle to operate the mechanical linkage mounted inside the lockset. This enables the user to retract a spring-biased latch bolt connected to the cylindrical lockset from a projected position extending outside the door and engaging a side slot formed in a doorjamb to a retracted position inside the door. The user is now free to swing the door on its hinges from a closed position to an opened position.
A locking mechanism of some kind is usually mounted in the cylindrical lockset. Such a locking mechanism is often actuated using a key or a button to lock or unlock the outside door handle. Typically, the locking mechanism is configured so that it can be actuated either by turning a key inserted into a keyway formed in the outside door handle or by turning or pushing a button mounted in the inside door handle. For example, cylindrical locksets using mechanical locking mechanisms are disclosed in U.S. Pat. Nos. 3,955,387 to Walter E. Best et al and 4,437,695 to William R. Foshee. Each of these locksets include a spring-loaded mechanical locking bar and turn button. The turn button is mounted in the inside doorknob and is operable to allow a user to actuate the mechanical locking bar and thereby control locking and unlocking of the outside doorknob.
It is also known to use a miniature motor and locking linkage mounted inside a cylindrical lockset to control locking and unlocking of the outside doorknob or handle. See, for example, U.S. Pat. Nos. 5,083,122 to Keith S. Clark and 5,018,375 to Clay E. Tully for descriptions of conventional electromechanical locking mechanisms.
It has been observed that there are problems that can affect the operation of many conventional motorized cylindrical locksets in the field over long periods of time. In part, this is because the electromechanical locking mechanisms included in such conventional locksets are very sensitive to variations in the on/off timing of the motor. Also, there is always the problem of motor stalling caused by overdriving the conventional electromechanical linkage should it encounter an unexpected obstruction and become bound up or jammed as it tries to move within the lockset between a door-unlocking position and door-locking position. For example, these conventional linkages can often become jammed if excessive torque is applied to the outside doorknob or handle manually by someone holding the outside knob or handle before and/or during the locking of the lockset using the electromechanical locking mechanism.
A motorized lock actuator able to move a locking lug or the like in a cylindrical lockset to lock or unlock a door handle without stalling or damaging the miniature lock actuator motor or impairing operation of the lockset would be a welcomed improvement over conventional motorized lock actuators. Moreover, cylindrical locksets could be improved by providing a motorized lock actuator having a compact size and simple construction and a configuration designed to fit inside conventional cylindrical locksets. Such a design would make it possible for current owners of many conventional fully mechanical cylindrical locksets to retrofit such locksets with new motorized lock actuators in accordance with the present invention without a lot of trouble or expense.
According to the present invention, an improvement is provided for use in actuating a locking means in a cylindrical lockset. The improvement includes means for moving the locking means between door handle locking and unlocking positions. The moving means includes a plunger having an axis, a locking-assist spring coupled to the plunger and the locking means, and means for reciprocating the plunger along its axis in opposite directions. To lock the cylindrical lockset, the reciprocating means moves the plunger along its axis in a locking direction against the locking-assist spring so that the locking-assist spring is moved toward the locking means to urge the locking means to its door handle-locking position. To unlock the cylindrical lockset, the reciprocating means moves the plunger along its axis in an opposite, unlocking direction away from the locking means so that the locking means is allowed to move to assume its door handle-unlocking position.
In preferred embodiments, the locking means includes a bushing and a locking lug coupled to the bushing. The bushing is able to reciprocate along the axis of the plunger and carry the locking lug between a handle-locking position wherein the locking lug locks a rotatable door handle to a fixed hub mounted in the door and a handle-unlocking position wherein the locking lug disengages the door-mounted hub to allow a user to rotate the handle relative to the door-mounted hub so that a latch bolt mounted in the door is retracted and the door can be opened.
Illustratively, the reciprocating means includes a rotatable spindle having a threaded distal end and a miniature motor for rotating the spindle about its axis. The plunger is an elongated rod having one end formed to include a blind threaded hole receiving the threaded distal end of the spindle. The opposite end of the plunger is arranged to extend into a central aperture formed in the reciprocable bushing. The locking-assist spring is a coiled compression spring winding around the plunger and having a first end abutting an external shoulder formed on the plunger and a second end abutting the reciprocable bushing.
In use, the motor is used to rotate the spindle which causes the plunger to advance in its locking direction due to the threaded connection between the spindle and the plunger. One unique aspect of the invention is that the plunger pushes the locking-assist spring to move the bushing and the locking lug mounted on the bushing far enough along the axis of the plunger so that the locking lug reaches its door-locking position. Ordinarily, the locking-assist spring will behave as a fairly stiff member and move the bushing in the locking direction in response to movement of the plunger in the same direction. However, the locking-assist spring is designed to be compressed between the plunger and the bushing whenever an obstruction blocks movement of the bushing in the locking direction and the motor continues to move the plunger against the spring and into the central aperture formed in the bushing. This compression causes a predetermined amount of potential energy to be stored in the locking-assist spring. Upon removal of the obstruction, the locking-assist spring is designed to decompress and move the now freely movable bushing and its locking lug to the handle-locking position.
Advantageously, obstruction of the bushing during locking or unlocking of the lockset is not expected to hinder movement of the plunger or impair operation of the motor or lockset. The motor always drives the plunger to a fully extended position in either the locking or unlocking direction every time the motor is actuated. This is possible because the plunger is coupled to the bushing by a compressible spring. Therefore, stalling of and damage to the motor and impairment of the operation of the lockset is minimized because of the novel way in which the motor is coupled to drive the bushing and the locking lug to its handle-locking position.
It will be understood that the so-called locking-assist spring functions to provide spring means for yieldably biasing the locking means (e.g., bushing and locking lug) toward its door handle-locking position. Preferably, another spring is included in the means for moving the locking means between door handle-locking and door handle-unlocking positions to provide spring means for yieldably biasing the locking means toward its door handle-unlocking position. This other spring is preferably a coiled compression spring that is located between the bushing and the door handle and functions to assist in moving the bushing in the unlocking direction. In use, if movement of the bushing in the unlocking direction is obstructed, the motor can still complete its cycle and move the spindle and plunger away from the obstructed bushing without stalling or damaging the motor or impairing the operation of the lockset. Later, upon removal of the obstruction, the unlocking-assist spring will decompress and move the bushing and its locking lug to the door handle-unlocking position to complete the unlocking of the cylindrical lockset.
The motor, rotating spindle, reciprocating plunger, and locking-assist spring in accordance with the present invention are easily mounted in certain conventional cylindrical locksets to permit such a lockset to be converted from a fully mechanical lock actuator to a motorized lock actuator in the field or in the shop. Most importantly, any obstruction of the locking lug as it moves in the cylindrical lockset between its door handle-locking and -unlocking position does not disrupt operation of the motor, rotation of the spindle, movement of the plunger, or operation of the locking-assist spring. This lengthens the life of the motor and minimizes disfunction of the motorized lock actuator.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.